Underground pipelines used to convey water, gas, sewage and other fluids have, in the past been constructed of clay tile, concrete, cast iron, ductile iron, steel or even wood. These pipelines have limited useful service lives due to deterioration of mechanical properties leading to leakage, collapse, ingress of external matter (soil), or blockages due to, foreign matter buildup as a result of internal discontinuities. In some cases, deterioration of mechanical properties may be due to chemical attack. For example, concrete pipe and cast iron and/or ductile iron pipe is susceptible to interior degradation, particularly at the “crown” of the pipe, due to the effect of hydrogen sulfide gas. In other cases mechanical or environmental factors may cause the deterioration. For example, tree roots may accelerate or cause degradation or blockages of underground lines. Deterioration may occur throughout the body of the pipe or at the connections between pipe segments.
Pipe lining is a process that was developed to enhance or prolong the useful life of pipelines, in particular, underground lines. The lining is typically installed in-situ in cases wherein the mechanical and physical properties of the pipe have degraded, but before total collapse. In some cases, the lining is installed when the pipe is new during the manufacturing process with the intention of providing a barrier between the conveyed product and the host pipe material. These linings provided enhanced performance and service life. However, just as the host pipes had a limited life span, typically measured in decades, so did many of the early lining systems. Many linings that slowed or stopped deterioration of the host pipes are now suffering from the same ills that plagued the original host pipes. In some cases blockages due to lining collapse have resulted where the bond between the lining and host pipe has failed or where foreign material has entered between the lining and host pipe.
Failure of a pipe lining presents a dilemma to the owners of pipe systems that have previously been lined using early technology lining systems. In most instances, the failing lining prevents the use of new lining technologies to repair the existing host pipe, leaving the owners with two options. The lined pipe may be burst (see Streatfield et al., U.S. Pat. No. 4,738,565) and a new pipe pulled in, with some added difficulty due to the lining. Alternatively, the entire length of the pipe may be excavated to remove and replace the existing pipe. However, the host pipe holds value in that it could possibly be lined by utilizing one of the new and improved technologies.
The use of mechanical devices to clean and maintain pipes has been limited to the removal of relatively loose debris and damaged lining. For example, a mechanical rotary device for removing old pipe linings is disclosed in Wentworth et al. Ser. No. 11/324,018, filed Dec. 30, 2005. However, often a ductile pipe will partially collapse or become twisted, and needs to be restored to a round profile before lining can be attempted. See also Harr U.S. Patent Publication 20050097689, May 12, 2005, which describes a tool for cleaning a culvert including a bucket attachment to a rod string for pushing or pulling debris out of the culvert. A need remains for a process and apparatus suitable for clearing solid obstructions, removing linings or liners from and repairing damaged or twisted pipelines, and provide of restoring the shape of pipelines that have been distorted. This overall maintenance would prolong the life well being of such pipelines. The present invention addresses this need.